Many agricultural combines use a rotary threshing and/or separating system. The system typically includes at least one rotor drivingly rotated within a rotor housing or cage including a perforated concave spaced radially outwardly thereof. The rotor will often have a frusto-conical inlet end having a helical flight or flights there around for conveying a flow of crop material into a space between the rotor and the rotor cage. The main body of the rotor will typically have an array or layout of threshing elements, typically rasp bars, which protrude radially outwardly into the space for conveying a mat of the crop material along a helical path through the space. Rasp bars cooperate with the rotor housing to separate larger components of the crop, namely crop residue commonly referred to as straw, which includes stalks, stems, cobs and the like, from the smaller grain and material other than grain.
Rasp bars are typically mounted to a support bracket on the rotor by a bolt. Worn rasp bars may be replaced by removing the bolt and attaching a new rasp bar to the support. Rasp bars are replaced in order to improve threshing efficiency and to avoid a rasp bar failure, which may significantly damage the combine.
The inventors have identified several problems with prior rasp bar designs. First, rough bolting surfaces on the rasp bars may cause an inconsistent translation of applied torque into effective clamp loading of the rasp bar to the rasp bar support that may lead to a rasp bar failure, which may significantly damage the rotor and rotor cage.
Second, rasp bar wear and retention during operation has become an issue due to increased rotor capacity and/or material flow. In particular, when impacted by harvested material such as corn, or by foreign material such as soil and/or rocks, the rasp bar may rotate about the rasp bar support bracket causing lost bolt tension and clamp load, leading to rasp bar retention failure.
Accordingly, there is a need for a rasp bar assembly that at least partially addresses the problems identified above. More specifically, there is a need for a rasp bar assembly having a bolting surface that facilitates an accurate translation of torque value measurement to clamp load during rasp bar attachment. Furthermore, there is a need for a rasp bar assembly having improved attachment stability that restricts the rotation of the rasp bar about the rasp bar support bracket.